1. Field of the Invention
This invention relates to an electric motor car controller for converting DC power collected from an overhead wire to AC power by a power converter and driving an AC motor.
2. Description of the Related Art
In the related art electric motor car controller, in order to remove impeding current contained in return current, first q-axis current iq1 is controlled by applying correcting amount dvq1 to q-axis voltage command vq1 based on voltage oscillation of a filter capacitor. A d-axis current id and the first q-axis current iq1 are found by rotational coordinate conversion based on the phase of the detected motor current.
It can be seen from a voltage equation (not described) on an AC motor in a d-q-axes-rotational coordinate system that d-axis and q-axis currents and magnetic fluxes are interrelated. That is, if only frequency ω1 is operated, the first q-axis current iq1 is controlled. In addition, d-axis current id, d-axis magnetic flux φd, and q-axis magnetic flux φq vary, producing interference. Accordingly, when the first q-axis current iq1 is controlled, variations in the d-axis current id and q-axis magnetic flux φq are suppressed by controlling the first q-axis current iq1 by the q-axis voltage vq, controlling the q-axis magnetic flux φq by the frequency ω1, and controlling the d-axis current id by the d-axis voltage vd (see, for example, JP-A-2002-238298 (page 5, page 7, and FIG. 6)).
In the related art electric motor car controller, a means for suppressing interference between d-axis and q-axis currents and magnetic fluxes is necessary. Therefore, there is the problem that the structure is made complex.
This invention has been made to solve the foregoing problem. The invention provides an electric motor car controller capable of reducing the harmonic components of return current by reducing the harmonic components contained in the amount of energy such that the amount of energy of a filter capacitor or filter reactor is treated as a subject of control.